As someone with ADHD, I would strongly advise that he pause plans of uni etc until he has either some really good strategies in place or medication (or both). Unless he has the option to redo bits of it, it is risky to attempt it when he's struggling with these difficulties. And even if he can redo, this can be discouraging if he makes friends on the course and then they all continue but he has to hang back a year or more. So it might help to put the brakes on a bit and wait until better support is in place. OTOH motivation/interest is really important with ADHD because it's so hard to drag yourself through tasks which are not interesting. So I can see both sides, which is why I'd say pause, not block entirely. If he's excited about and interested in the course, then it's likely to be a better option than something closer to home that he's less interested in.
It's a really common cycle I think with ADHD, my DS1 is going through it too, because you tend to look back at what's happened and you can usually pinpoint what you should have done differently, and so you assume, oh I just wasn't taking it seriously/I wasn't trying hard, but next time I will try harder, I will make myself do it and it will be OK.
The problem is that the reason they don't do the sensible thing in the first place is executive dysfunction, and the brain is very good at rationalising these bad choices so they make sense to the person in the moment. So it becomes oh just this once I can skip the lecture (becomes skipping more than half), oh I have a headache, I'll get the slides/recording later (never actually gets round to it), I can't concentrate on this essay now, I'll finish it tomorrow (can't concentrate any better tomorrow, or forgot about social event they can't possibly miss, or got distracted and suddenly remembered essay is due too late). So you get to the end of the line and go fuuuuck. Well that was stupid, I should have gone to the lectures and done the essay earlier. I'll retake it and do it right this time.
Repeat ad infinitum. The problem is that the issue is two or threefold - they don't properly recognise patterns of why they are making bad choices. So they know what they "should" do but don't do it, and don't really understand why they don't do it. Everything seems to make sense individually but taken as a whole even the person with ADHD can see that it's a mess and looks like they aren't trying. This then leads to a depression type response where they don't understand why it never works out and they can't make changes, they start to feel worthless, it can be quite a crushing cycle.
Before I was diagnosed I kept saying look, I know what I'm saying sounds like depression (I'm useless, I never finish anything, I can't reach my potential, I am a terrible friend) but I couldn't understand it because I didn't FEEL depressed and I also knew that what I was saying was true. OK, I accept now that I was never useless even at my least functioning, and I was never a terrible friend although I could be unreliable.
Understanding the ADHD brain and how it works can help a lot because you can start to see the patterns in where you're going wrong and put things in place to combat them. A lot of the time, things which work for NT people such as making a list do not work because ADHD makes it hard to use tools like that. As you've said, I would make lists and then not do anything with the list. I still don't really understand how to use to-do lists at the age of 37, though I am a bit more successful at using them than my younger self was.
I had so many problems with lists - I would forget to put items on the list. I would lose the list. I would lose a pen and give up writing on it. I would forget the list existed. It would not occur to me to look at the list at the right time (I still struggle with this one).
For university I found the best thing was having a big wall calendar and mapping out when my essays were due and extending this back a few weeks so I knew when I needed to be working on things, and adding extra time if two overlapped.
For household stuff I have to have it set on a schedule, not a detailed one, but a rough one so I know what I'm meant to be doing when and it has to have a kind of logic to it - e.g. my washing machine is in the bathroom (I'm abroad) so I always stick in a load when I first wake up to keep it moving. And I know I have to go to the supermarket on Thursdays or I won't have time to do it on any other day, or e.g. in the past I've chained things to other things like doing a shop on the day that I have a course in a location near the shop because it saves me an extra trip out, and that's much easier for me than getting the motivation together to leave the house when I don't technically "have to".
Dr. Russell Barkley was game changing for me - he has a lot of informative presentations on Youtube, although some people find him a bit depressing, I really appreciate the way he spells out what people with ADHD struggle with and how that translates to everyday life. Understanding things like this helped me with workarounds. He is very big on ADHD not being a disorder of not KNOWING what to do, but of not DOING what you KNOW. And reframing it like this is helpful because it stops me looking for magic solutions that I will be able to follow. I already know what to do, that wasn't the problem. My problem is getting myself to do what I know I need to do.
For example, I no longer kid myself that I will have magic endless energy, time and motivation "later" because I recognise that as a false thought. (I know a lot of young people struggle with understanding this as well - but it is life-ruiningly extreme, pathological in fact, in ADHD).
How To ADHD is another good youtube channel because she has short and engaging and positive videos on specific topics, and is well researched.